U.S. patent application number 14/040000 was filed with the patent office on 2015-04-02 for receiver chip with multiple independent loop-through paths.
This patent application is currently assigned to SILICON LABORATORIES INC.. The applicant listed for this patent is SILICON LABORATORIES INC.. Invention is credited to Russell Croman, Navin Harwalkar, Dan B. Kasha, Mark W. May, Mike R. May, Tim Stroud.
Application Number | 20150094007 14/040000 |
Document ID | / |
Family ID | 52740636 |
Filed Date | 2015-04-02 |
United States Patent
Application |
20150094007 |
Kind Code |
A1 |
Kasha; Dan B. ; et
al. |
April 2, 2015 |
Receiver Chip with Multiple Independent Loop-Through Paths
Abstract
A radio receiver and method of operating the same are disclosed.
In one embodiment, the radio receiver may include a RF receive path
configured to convey a first radio signal within a first band to a
radio tuning circuit. The RF receive path may be controllable using
a first AGC circuit. The radio receiver may also include a
loop-through path configured to convey a second radio signal within
a second band between an input and an output of the radio receiver.
The second band may be different from the first band. The
loop-through path may be controllable using a second AGC
circuit.
Inventors: |
Kasha; Dan B.; (Seattle,
WA) ; Croman; Russell; (Buda, TX) ; May; Mike
R.; (Austin, TX) ; May; Mark W.; (Austin,
TX) ; Harwalkar; Navin; (Austin, TX) ; Stroud;
Tim; (Austin, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SILICON LABORATORIES INC. |
Austin |
TX |
US |
|
|
Assignee: |
SILICON LABORATORIES INC.
Austin
TX
|
Family ID: |
52740636 |
Appl. No.: |
14/040000 |
Filed: |
September 27, 2013 |
Current U.S.
Class: |
455/240.1 |
Current CPC
Class: |
H03G 3/3052
20130101 |
Class at
Publication: |
455/240.1 |
International
Class: |
H03G 3/30 20060101
H03G003/30 |
Claims
1. A radio receiver comprising: a radio frequency (RF) receive path
configured to convey a first radio signal within a first band to a
radio tuning circuit, wherein the RF receive path is controllable
using a first automatic gain control (AGC) circuit; and a
loop-through path configured to convey a second radio signal within
a second band between an input and an output of the radio receiver,
wherein the second band is different from the first band, and
wherein the loop-through path is controllable using a second AGC
control circuit.
2. The radio receiver as recited in claim 1, wherein the
loop-through path is further configured to convey a radio signal,
within the first band, on the loop-through path.
3. The radio receiver as recited in claim 1, further comprising a
plurality of loop-through paths each having an input and an output,
the plurality of loop-through paths including the loop-through
path, wherein each of the loop-through paths provides a signal path
between its respective input and respective output, and wherein a
gain through each of the loop-through paths is separately
controllable using AGC circuitry.
4. The radio receiver as recited in claim 3, wherein each of the
plurality of loop-through paths is configured to pass signals in a
one of a plurality of different bands wherein the plurality of
bands includes two or more of the following: a frequency modulation
(FM) band; an amplitude modulation (AM) band; digital audio
broadcast (DAB) L-band; and DAB band III.
5. The radio receiver as recited in claim 3, wherein the RF receive
path is coupled to one of the plurality of loop-through paths, and
wherein the radio receiver further comprises a selection circuit
having a plurality of inputs each coupled to a corresponding one of
the plurality of plurality of loop-through paths and an output
coupled to the radio tuning circuit, wherein the selection circuit
is configured to couple a selected one of the plurality of
loop-through paths to the radio tuning circuit.
6. The radio receiver as recited in claim 1, wherein the radio
receiver is configured to convey a radio signal in the amplitude
modulated (AM) band on the loop-through path.
7. The radio receiver as recited in claim 1, wherein the radio
tuning circuit includes: a local oscillator configured to generate
a periodic signal, wherein the periodic signal has a selectable
frequency; a mixer coupled to receive the periodic signal and
further configured to receive the first signal, wherein the mixer
is configured to down-convert the first radio signal to an
intermediate frequency (IF) signal.
8. The radio receiver as recited in claim 1, wherein power for each
of the tuning and loop-through paths are each separately
controllable from one another.
9. A method comprising: conveying a first radio signal in a first
band to a radio tuning circuit via a radio frequency (RF) receive
path; controlling a gain of the first radio signal using first
automatic gain control (AGC) circuitry; conveying a second radio
signal in a second band on a loop-through path between an input and
an output of the radio receiver, wherein the second band is
different from the first band; and controlling a gain of the second
radio signal using second AGC circuitry.
10. The method as recited in claim 9, further comprising conveying
the second radio signal in the first band on the loop-through
path.
11. The method as recited in claim 9, further comprising: conveying
radio signals through two or more of a plurality of loop-through
paths each having an input, an output, and corresponding AGC
circuitry; controlling a gain in at least one of the plurality of
loop-through paths, using its AGC circuitry, separate from the
other ones of the plurality of loop-through paths.
12. The method as recited in claim 9, wherein the first band and
the second band are selected from the following bands: a frequency
modulation (FM) band; an amplitude modulation (AM) band; digital
audio broadcast (DAB) L-band; and DAB band III.
13. The method as recited in claim 9, wherein the second band is an
amplitude modulated (AM) band on the loop-through path.
14. A radio receiver comprising: a plurality of loop-through paths
each having an input and an output, wherein each of the
loop-through paths provides a signal path between its respective
input and respective output, and wherein a gain through each of the
loop-through paths is separately controllable using automatic gain
control (AGC).
15. The radio receiver as recited in claim 14, wherein each of the
plurality of loop-through paths includes a corresponding low noise
amplifier (LNA), wherein the LNA of each of the plurality of
loop-through paths includes an input coupled to the input of its
corresponding loop-through path.
16. The radio receiver as recited in claim 15, wherein each of the
plurality of loop-through paths includes a corresponding buffer
circuit having input coupled to an output of the corresponding LNA
of that loop-through path and an output coupled to the output of
its corresponding loop-through path.
17. The radio receiver as recited in claim 14, wherein each of the
plurality of loop-through paths is configured to pass signals in a
unique one of a plurality of frequency bands.
18. The radio receiver as recited in claim 17, wherein the
plurality of bands includes two or more of the following: a
frequency modulation (FM) band; an amplitude modulation (AM) band;
digital audio broadcast (DAB) L-band; DAB band III.
19. The radio receiver as recited in claim 14, wherein power for
each of the plurality of loop-through paths is separately
controllable.
20. The radio receiver as recited in claim 14, wherein the
plurality of loop-through paths is implemented on a single
integrated circuit.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] This disclosure relates to integrated circuits, and more
particularly, integrated circuits used in radio equipment.
[0003] 2. Description of the Related Art
[0004] In recent years, radio tuners/receivers have been designed
with increasing numbers of features. Specifically, radio broadcast
has expanded beyond traditional AM/FM radio, and now includes HD
radio, DAB radio and DRM standards. Further, additional frequency
spectrum can be used in some radio standards, such as DAB's use of
Lband. These new frequency channels add additional hardware
complexity to optimize system performance. Finally, multiple
antennas can be used to improve the performance of the radio
system. Thus, with increasing complexity of radio systems, new
architectures are needed to deliver high quality services to the
customer.
[0005] FIG. 1 (Prior Art) is a diagram illustrating one embodiment
of a radio capable of operating multiple tuners concurrently. In
the embodiment shown, Tuner #1 includes an amplitude modulation
(AM) tuning circuit and an FM tuning circuit. The AM and FM tuning
circuits may each include a mixer and a local oscillator. A
multiplexer (`Mux`) is coupled to the outputs of both tuning
circuits, and may select one for further processing as the received
signal by Tuner #1. Automatic gain control (AGC) circuitry is
implemented in Tuner #1, and may provide gain control for the band
selected by the multiplexer.
[0006] Tuner #1 also includes a loop-through path for the FM input.
That is, the FM signal may pass through an LNA and a buffer to an
output which is coupled to an input of Tuner #2. Although the
signal may pass through both an LNA and a buffer, it is
nevertheless not subject to AGC. Instead, the FM signal may be
gain-controlled by Tuner #2 after receiving it from the
loop-through output of Tuner #1.
SUMMARY OF THE DISCLOSURE
[0007] A radio receiver and method of operating the same is
disclosed. In one embodiment, the radio receiver may include a
radio frequency (RF) receive path configured to convey a first
radio signal within a first band to a radio tuning circuit. The RF
receive path may be controllable using a first AGC circuit. The
radio receiver may also include a loop-through path configured to
convey a second radio signal within a second band between an input
and an output of the radio receiver. The second band may be
different from the first band. The loop-through path may be
controllable using a second AGC circuit.
[0008] In one embodiment, a method includes conveying a radio
signal in a first path to a radio tuning circuit via a tuning path.
The method further includes controlling the gain of the first radio
signal using first AGC circuitry. The method further includes
conveying a second radio signal in a second band on a loop-through
path between an input and an output of the radio receiver, with the
second band being different from the first band. The gain of the
second radio signal is controlled using second AGC circuitry.
[0009] In one embodiment, the receiver may be implemented on a
single integrated circuit chip. Each of the loop-through paths may
include a low noise amplifier (LNA) and may also include a buffer
circuit (e.g., an amplifier designed to drive an output pin). Radio
frequency (RF) signals may be conveyed through each of the
loop-through paths, from input to output, simultaneously or
concurrently, with each of the loop-through paths being under AGC
separately from the other loop-through paths (i.e. each
loop-through path includes separate AGC circuitry). Each of the
loop-through paths may be configured for conveying signals from a
unique one of a number of different frequency bands. The receiver
circuit may also function as a primary tuner/receiver for one of
the bands. A selection circuit may be used to select the band to be
conveyed to the primary tuner/receiver on the chip, while other
received bands may pass through their respective loop-through
paths. The band selected to be conveyed by the primary
tuner/receiver may also pass through a loop-through path.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Other aspects of the disclosure will become apparent upon
reading the following detailed description and upon reference to
the accompanying drawings which are now described as follows.
[0011] FIG. 1 (Prior Art) is a block diagram of one embodiment of a
radio having two tuners.
[0012] FIG. 2 is a block diagram illustrating one embodiment of a
receiver having a RF receive path and a loop-through path.
[0013] FIG. 3A is a block diagram illustrating of one embodiment of
a receiver chip.
[0014] FIG. 3B is a block diagram illustrating another embodiment
of a receiver chip.
[0015] FIG. 4 is a diagram illustrating the arrangement of an
automatic gain control apparatus in one embodiment of a receiver
chip.
[0016] FIG. 5 is a flow diagram illustrating one embodiment of a
method for operating a receiver chip having multiple loop-through
paths.
[0017] While the subject matter disclosed herein is susceptible to
various modifications and alternative forms, specific embodiments
thereof are shown by way of example in the drawings and will herein
be described in detail. It should be understood, however, that the
drawings and description thereto are not intended to be limiting to
the particular form disclosed, but, on the contrary, is to cover
all modifications, equivalents, and alternatives falling within the
spirit and scope of the present disclosure as defined by the
appended claims.
DETAILED DESCRIPTION
[0018] FIG. 2 is a block diagram illustrating one embodiment of a
receiver implemented on an integrated circuit chip. In the
embodiment shown, receiver 20 includes two inputs, a first input
for Band 1 and a second input for Band 2. Signals received through
the Band 1 input may be received in a first radio band, while
signals received through the Band 2 input may be received in a
second radio band that is different than the first. As used in
here, the term "different" with respect to two or more radio bands
indicates that these bands each occupy a unique range of
frequencies. For example, Band 1 may receive signals in the FM
band, while Band 2 may receive signals in the AM band. Other bands
are possible and contemplated, such as digital audio broadcast DAB
L-band and DAB band III, among others.
[0019] The Band 1 input in the embodiment shown is received into a
RF receive path. In this particular example, the RF receive path
implements a heterodyne receiver in which the RF signal is down
converted to an IF signal before further processing and final
conversion to a baseband signal. It is noted however that
embodiments implementing a zero IF conversion receiver architecture
are also possible and contemplated, and thus the heterodyne example
shown here is not intended to be limiting. The RF receive path
includes a first low noise amplifier (LNA) 21-1, AGC circuitry
24-1, a mixer 25 that is coupled to receive a signal from a local
oscillator 26, an IF amplifier 28, an analog-to-digital converter
(ADC) 29 and a digital signal processor 30. An IF signal received
from IF amplifier 28 may be converted into digital data by ADC 29
and further processed (including conversion to baseband) by DSP 30.
Although not explicitly shown, DSP 30 may be coupled to output the
processed data to other circuitry that may be internal or external
to receiver 20 (e.g., a digital-to-analog converter, or DAC, for
converting the digital data to audio for output to speakers). Some
embodiments may not have an ADC and DSP and may instead output the
IF as an analog signal for processing in another IC or circuit.
[0020] The Band 2 input in the embodiment shown is coupled to a
loop-through path 23. The loop-through path 23 in the embodiment
shown includes a second LNA 21-2, AGC circuitry 24-2, and a buffer
22-2, which is coupled to the Band 2 loop-through output. AGC
circuitry 24-2 is configured to automatically control the gain of
the Band 2 radio signal separate from AGC 24-1 in the RF receive
path. In general, various embodiments of receiver 20 implement
multiple instances of AGC circuitry 24, each of which may operate
separately from one another. As will be discussed, embodiments
having multiple loop-through paths that are each gain controlled
using dedicated instances of AGC circuitry 24 may be implemented to
allow multiple loop-through paths to provide a gain controlled
output signal. Alternate embodiments may also include combining the
functionality of LNA 21-2 and buffer 22-2 into a single amplifier
stage, where the AGC 24-2 adjusts the gain of the composite
amplifier. Another alternate embodiment of the circuitry shown in
FIG. 2 may be implemented such that the AGC function may be
co-mingled with the amplifier function so that, for example, the
gain of the LNA is adjusted based on the signal size.
[0021] While embodiments are possible and contemplated wherein a
receiver is implemented using discrete components or separate
integrated circuits (ICs), receiver 20 as shown herein may be
implemented on a single IC die. Accordingly, such an IC may include
multiple, separate paths each under the control of a dedicated
instance of AGC circuitry 24 that operates separately from AGC
circuitry in the other paths. This in turn may enable a number of
different signal paths associated with corresponding different
bands to be implemented on a single IC die.
[0022] Tuning now to FIG. 3A, a block diagram of another embodiment
of a receiver 20 is illustrated. Receiver 20 in this example is
coupled to receive a number (N) of different radio signals from
band splitting circuitry 19. In turn, band splitter circuitry may
receive radio signals from antenna elements 17, which may comprise
one or more antennas. It is noted that receiver 20 may also receive
radio signals via other mechanisms, such as through a splitter
coupled to a coaxial cable, to use one example. In another example
implementation, one or more inputs of a receiver 20 may be coupled
to loop-through outputs of another receiver, such as another
instance of receiver 20.
[0023] In the embodiment shown, receiver 20 includes N inputs and N
loop-through paths 23. For example, the Band 1 input may convey a
radio signal into loop-through path 23-1, Band 2 may convey another
radio signal into loop-through path 23-2, and so forth. Each
loop-through path 23 includes a corresponding LNA 21, buffer 22,
and AGC circuitry 24 (e.g., LNA 21-1, buffer 22-1, and AGC 24-1 in
loop-through path 23-1).
[0024] Each of the AGC circuits 24 may operate separately from the
others. For example, AGC 24-1 may provide AGC for a Band 1 radio
signal received via LNA 21-1, while AGC 24-2 may provide AGC for a
Band 2 signal received via LNA 21-2. Furthermore, receiver 20 is
configured such that multiple loop-through paths may operate
simultaneously, each conveying a signal within its specified band.
Additionally, one of the loop-through paths may be selected for
coupling to a corresponding mixer 25 and may thus act as the main
RF receive path for receiver 20 during the time that other
loop-through paths are operating. Furthermore, the path used as the
main RF receive path may at the same time have its loop-through
path conveying its signal to its corresponding loop-through
output.
[0025] The use of multiple loop through paths and a main RF receive
path simultaneously may thus be enabled by the used of separate
instances of an AGC circuit 24 for each loop-through path 23. It is
noted that specific instances of an AGC circuit 24 may be different
from others. For example, since AGC 24-1 is configured to perform
AGC for radio signals received in Band 1, it may have a different
circuit topology and/or use components having different values than
AGC 24-2, which is used for performing AGC for radio signals in
Band 2. In general, a given band may have noise and/or linearity
requirements that are unique to that band. Thus, the corresponding
circuitry for a given band, including the AGC circuitry, may be
specially configured for that band. In prior art embodiments in
which the loop-through paths are not separately controlled using
AGC, it may not be possible to pass multiple signals in multiple
different bands.
[0026] The bands received through the various inputs may be
different from one another. However, it is possible in some
embodiments that multiple inputs may be provided for the same band.
Furthermore, circuitry in some embodiments of receiver 20 may be
re-configured to receive different bands at different times.
[0027] Receiver 20 includes a number of mixers, 25-1, 25-2, etc.,
up to 25-N. A local oscillator 26 is coupled to each of the mixers
25. The frequency of a signal provided by the local oscillator 26
may be variable in order to downconvert a radio signal in a
selected band. The output of each mixer 25 may be coupled to an
input of a selection circuit 27. The selection circuit 27 is
coupled to receive one or more selection signals to cause one of
the inputs to be selected. When a particular input is selected, its
corresponding path in receiver 20 may become the RF receive path in
use at that particular time, even if the corresponding loop-through
path 23 is also being used. When a particular input of selection
circuit 27 is selected, the path from the input to DSP 30
effectively becomes the RF receive path for receiver 20.
[0028] The output of selection circuit 27 is coupled to IF
amplifier 28, which performs amplification of an IF signal. While
the embodiment shown in FIG. 3A is implemented as a heterodyne
receiver, other embodiments implementing a zero-IF receiver
architecture are possible and contemplated. In such embodiments, IF
amplifier 28 may be replaced with a baseband amplifier or other
appropriate circuitry. The output of IF amplifier 28 in FIG. 3A is
coupled to ADC 29, which converts the received signal to a digital
format and provides a corresponding stream of digital data to DSP
30 for further processing. However, as noted above, some
embodiments may be implemented such that the output of IF amplifier
28 is processed as an analog signal instead of being converted into
a digital format. Moreover, embodiments are possible and
contemplated wherein all back end processing is conducted in the
analog domain rather than converting to digital.
[0029] FIG. 3B is another embodiment of a receiver 20. More
particularly, FIG. 3B illustrates an embodiment that is one
specific implementation of the more general embodiment shown in
FIG. 3A. In the embodiment shown in FIG. 3B, receiver 20 includes
four loop-through paths 23. Each loop-through path 23 is configured
to convey signals on a band that is unique with respect to that of
the other loop-through paths 23. Loop-through path 23-1 is
configured to convey signals in the DAB L-Band. Loop-through path
23-2 is configured to convey signals in DAB Band III. Loop-through
path 23-3 is configured to convey signals in the FM band.
Loop-through path 23-4 is configured to convey signals in the AM
band. It is noted that the use of these bands is exemplary, is not
intended to be limiting, and that other embodiments may include
loop-through paths for conveying signals in other bands not
discussed herein.
[0030] Similar to the embodiment shown in FIG. 3A, receiver 20 of
FIG. 3B includes a number of mixers (25-1, 25-2, 25-3, and 25-4), a
local oscillator 26 coupled to provide a signal to each of the
mixers, a selection circuit 27 coupled to the output of the mixers,
an IF amplifier 28, an ADC 29, and a DSP 30. Using selection
circuit 27, one of the bands can be selected for further processing
by receiver 20. This further processing may occur simultaneously
while at least one of the loop-through paths 23 passes a radio
signal in its corresponding band between its input and output.
[0031] In some instances, not all of the loop-through paths 23 are
used during operation of receiver 20. In such instances, it may be
desirable to power down components that are not in use. In the
embodiment of FIG. 3B, receiver 20 includes a power control unit
33, which may be implemented using hardware, software, or a
combination of the two. Power control unit 33 may monitor the
status of various components in receiver 20 and may remove power
from those that are not currently in use (it is noted that the
actual connections are no shown here for the sake of simplicity).
For example, if none of the circuitry in a given one of the
loop-through paths 23 is in use, power control unit 33 may remove
power from its corresponding LNA 21, the corresponding buffer 22,
and corresponding AGC circuitry 24. In general, power control unit
33 may allow power to be provided or cause power to be removed from
various ones of the circuits on the IC upon which receiver 20 is
implemented. Furthermore, power for each of the loop-through paths
23 may be controlled separately, and thus powering down of one
loop-through path 23 need not affect the others. Powering down
unused circuitry may have a number of benefits, including power
savings, lower thermal outputs, and a reduction of noise that can
affect those circuits that remain powered on. Furthermore, power
control unit 33 may adjust the power consumption of each
loop-through path in such that it is reduced without completely
removing power therefrom. This may ensure that overall chip power
consumption remain within desired limits, while also enabling the
loop-through paths to remain powered on. Since power can be
adjusted for each loop through path independently of one another,
the power and performance of each path may be controlled as
needed.
[0032] Turning now to FIG. 4, a diagram illustrating one embodiment
of AGC circuitry 24 is shown. Since the AGC circuitry 24 is
distributed in this embodiment, the elements comprised thereby
include attenuators 241-1 and 241-2, RF level detector 242, and AGC
controller 245. The other elements shown in the drawing, namely LNA
21 and buffer 22, are not considered to be part of AGC circuitry
24. It is noted that the AGC circuitry illustrated herein is but
one embodiment of circuitry that may be used to implement AGC in
the various loop-through paths 23 of a receiver 20 as discussed
above. However, numerous other embodiments of AGC circuitry are
possible and contemplated. It is further noted that AGC circuitry
may be configured for operation with a particular frequency band,
and thus the different loop-through paths may have different
implementations of AGC circuitry with respect to each other. In
some implementations attenuator 241-1 and LNA 21 could be combined,
and similarly attenuator 241-2 and buffer 22 could be combined. The
overall function of adjusting the signal level through the
corresponding amplifier to prevent distortion remains the same.
[0033] In the embodiment shown, RF level detector may detect a
signal level of an RF signal following its output from LNA 21. The
detected RF level may be used as feedback. The detected RF level
may be reported to AGC controller 245. AGC controller 245 may in
turn set gain levels in LNA 21 and buffer 22, as well as setting
attenuation levels in attenuators 241-1 and 241-2. As detected RF
levels change, AGC controller 245 may continue to make gain and
attenuation adjustments.
[0034] FIG. 5 is a flow diagram illustrating one embodiment of a
method for operating a receiver chip having multiple loop-through
paths. Method 500 may be implemented using any embodiment of
receiver 20, including those discussed above as well as those not
discussed herein.
[0035] Method 500 includes a radio receiver chip receiving RF
signals on at least two different inputs (block 505). The radio
receiver chip may include at least one loop-through paths coupled
to one of the inputs and at least one RF receive path coupled to
another one of the inputs. In some embodiments, such as those shown
in FIGS. 3A and 3B above, an input may be coupled to a loop-through
path, but may also become coupled to downconversion and back end
processing circuitry to form a RF receive path. In some
embodiments, the inputs may correspond to different frequency
bands, although this is not necessary for all embodiments. The
maximum number of inputs and corresponding loop-through paths may
vary from one embodiment of the receiver chip to another.
[0036] Method 500 further includes using AGC on each of the tuning
and loop-through paths (block 610). The tuning and loop-through
paths may be separately controllable using AGC, each having its own
dedicated AGC circuitry. AGC circuitry may be used to adjust gain
levels of an LNA in the RF receive path. In a loop-through path,
AGC circuitry may be used to adjust gain levels of a buffer. AGC
circuitry may also be used to adjust the levels of attenuators that
may be implemented in the tuning and loop-through paths.
[0037] Numerous variations and modifications will become apparent
to those skilled in the art once the above disclosure is fully
appreciated. It is intended that the following claims be
interpreted to embrace all such variations and modifications.
* * * * *